Between 20% and 50% of pregnancies end in miscarriage. These numbers cannot be exactly detectable for the reason already mentioned: symptoms of miscarriage during the early stages of pregnancy are very hard to detect. However, when pregnancy is detected approximately 10% of pregnancies ends in miscarriage, and if this happens, it is between the 7th to 12th weeks of pregnancy. For most miscarriages there is no known cause, some are caused because of complications and defects in the chromosomal development of the fetus, while other miscarriages are caused by infections, traumas, anatomical abnormalities and certain systemic diseases, such as diabetes. Of course, some miscarriages are caused because of risky lifestyle habits such as alcohol drinking, smoking, drug abuse and even caffeine drinks.
On the other hand, it is a misconception that sexual intercourse or exercise can cause abortion. As already mentioned signs of miscarriage during the early stages of pregnancy have very few symptoms or even no symptoms. The most common sign of miscarriage includes vaginal spotting, bleeding and cramps. A lot of times early miscarriage can be mistaken for a menstrual period. Woman might also experience passing a tissue through the vagina or fluid leaking. In cases clotty tissue passes, tissue should be taken to a doctor for examination. During miscarriage woman might also experience abdominal pain or low back pain.